1. Field of the Invention
My invention relates to electric motor control systems, and particularly to means for operating an electric motor of predetermined rated voltage (or voltage range) at line voltages continuously above the highest motor voltage rating.
2. Description of the Prior Art
Household appliances, such as refrigerators, dishwashers, washing machines and the like include electric motors of selected standard ratings designed to operate without undue temperature rise at a supply voltage of predetermined magnitude, or at voltages within a predetermined range of magnitudes. Normal source voltages at some locations are somewhat different than at others, and may be continuously or frequently above the rated voltage, or voltage range of the standard motor of nearest rating. A motor connected directly to such a source will overheat in operation. In order to avoid the need for special motors in applications where supply voltage varies widely or normally exceeds the voltage rating of an available standard motor it is desirable to provide means for operating a motor of predetermined voltage rating from a supply source having a voltage greater in magnitude than the highest motor voltage rating.
Accordingly, it is a principal object of my invention to provide improved control means for operating an electric motor without overheating from a source of electric current supply having a voltage magnitude normally or frequently above the highest rated voltage of the motor.
It is a more specific object of my invention to provide an improved motor control circuit for electric dishwashers of the "static" cycle type having an electric driving motor and an electric heating coil operable during non-overlapping time intervals.